1. Field of the Invention
The invention relates to a projection type display device which separates a white beam from a light source into beams of three colors, i.e., red, blue and green, modulates each color beam through a light valve such as a liquid crystal panel in accordance with image information, synthesizes the modulated color beams by light synthesizing means, and projects the synthesized beams onto a projection surface through projecting means in an enlarged state. More specifically, the invention relates to a mechanism for mounting a liquid crystal panel to a prism composite constituting a light synthesizing mechanism of a projection type display device.
2. Description of Related Art
In a conventional projection type display device, a liquid crystal panel, serving as a light valve, is mounted to a light incident surface for each light beam of a prism composite. The prism composite is a light synthesizing mechanism. A conventional mechanism for mounting a liquid crystal panel to a prism composite is disclosed in Japanese Unexamined Patent Publication No. 6-118368. In this type of mounting mechanism, the liquid crystal panel, which serves as the light valve, is directly glued and fixed to the light incident surface of the prism composite by an adhesive.
When the light valve is directly glued and fixed to the light incident surface, it is possible to omit the mutual pixel matching mechanism (alignment) of multiple light valves which modulate the light beam separated into red, green and blue colors. It is also possible to omit the focus adjusting mechanism (focus adjustment) so that each image formation plane constituting the subject is positioned within the permissible depth of focus of the projection lens. Thus, it is possible to reduce the size, weight and number of parts of the optical system of the projection device.
However, when the light valve is directly glued and fixed to the light incident surface of the prism composite, several problems may arise. These problems are outlined below.
First, when external light enters the interior of the device, there is a possibility that the external light will enter the light valve. When the light valve receives such light, there is also a possibility of each element of the light valve malfunctioning.
Second, directly touching the light valve while treating the light valve is not desirable since that will lead to problems such as breakage. For example, when the light valve is glued to the prism composite, chucking the light valve directly with a jig may lead to the edge, corner, etc. of the light valve being damaged. Additionally, it is not desirable for the operator to hold the light valve directly by hand and glue it to the prism composite because the light valve, such as a liquid crystal panel, is also vulnerable to static electricity.
Third, the light valve, which is glued to the prism composite, can generate a defect in a part of its pixels as a result of changes with time. When a defect has been generated in the light valve, it is necessary to replace it with a new one. However, since the light valve is glued and fixed to the prism composite, it is difficult to replace only the light valve having the defect. That is, it is not easy to detach the liquid crystal panel glued and fixed to the light incident surface of the prism composite without damaging the light incident surface. For this reason, it is necessary in some cases to also replace the prism composite. The replacement of the prism component, however, is not economical.